The LASIR system of instruments provide a way of measuring specific pollutants with no interferences form other gases. Since they are based on laser diodes operating in the communication region of the near infrared, they are rugged, easy to operate and relatively small and inexpensive. The instrument can be located in any desired location where it is free of environmental constraints and is readily available for servicing if required. The monitoring beam is transmitted to the measuring location by fiber optics. In some configurations the delivery optics contain no electrical components and can be placed in explosive or hazardous locations. These measurements locations can be up to several kilometers distant from the control. Three versions of the LASIR are available, (1) the LASIR-R for perimeter or area ambient air monitoring, (2) the LASIR-P for point source measurements, and (3) the LASIR-S for in stack monitoring. Multiplexing can be used to operate, simultaneously, a combination of a number of these versions for mt he same instrument at a number of locations, and if desired, with a variety of different lasers. Examples of the application of these system for measuring HF in aluminum smelters have shown that there is ample sensitivity to measure HF both in the stacks and in the pot-rooms of these smelters.